[Preprint] Differences and Similarities between Developmental Coordination Disorder and Attention-Deficit/Hyperactivity Disorder: A Scoping Review

Developmental Coordination Disorder and Attention-Deficit Hyperactivity Disorder are common neurodevelopmental disorders that often co-occur and have similar secondary symptoms. While DCD and ADHD are considered separate conditions, their commonalities create challenges for differential diagnosis and support. Therefore, this preregistered broad-spanning scoping review includes systematic literature searches to summarize all available studies on DCD and/or ADHD. N = 68 articles were classified into the following categories: (i) neuroimaging, (ii) genetic and twin studies, (iii) methylphenidate, (iv) cognition, (v) motor skills, (vi) physical activity and physical therapy, (vii) perception, sensory processing, and visuomotor integration, (viii) psychosocial factors and wellbeing, and (ix) symptom presence and management. Most studies included samples under 18 years old and almost no studies were replicated. Common themes supported that individuals with co-occurring DCD and ADHD have more difficulties than those with one condition. While we found numerous neural and functional overlaps between DCD and ADHD, several features consistently differentiated the conditions, e.g., sensorimotor difficulties in DCD. Thus, we conclude that DCD and ADHD are similar conditions with a few differential features, however, co-occurring DCD+ADHD has unique burdens not observed in either condition alone. Extensive replication is needed to determine the precursors, stability, and changeability of DCD and/or ADHD.